Method of roasting and reducing ores



Oct. 22, 1929. cHRlSTlANsEN 1,732,672

METHOD OF ROASTING AND REDUCING ORES Filed Jan. 6, 1928 Patented Oct.22, 1929 BROB'CHBISTIANSEN, OF SMEDJ'EBACKEN, SWEDEN METHOD OFROAS'I'IN'G Application filed January 6, 1928, Serial No.

In my copending application Ser. No. 98,347 I have described a method ofreducing ores, especially iron ores,in which the ore loaded on carriagesis fed'through a channel furnace'and subjected successively topreheating, roasting, prereduction and final reduction operations. Insaid method the final reduction of the ore is carried out by means ofcirculating reducing gases which outside the furnace are regenerated bymeans of alternately operative recarbonizing furnaces, the excess of gasformed in the circulation system being drawn oil and partially combustedin the momentarily inoperative recarbonizing furnace by a regulatedsupply of air for reheating said furnace and the combustion gasesescaping from said latter furnace being supplied to the pre-reductionzone of the channel furnace and finally combusted by an excess of air inthe roasting and preheating zones.

The chief object of this invention is to modify said method in order toobtain a more rapid and effective reheating of the momentarilyinoperative recarbonizing furnace, the modification consisting, chiefly,in this that the reheating of said recarbonizing furnace is effected bysuch a plentiful supply of combustion air that the combustion gasesescaping from said furnace consist essentially of carbon dioxide andnitrogen, said c0mbus-- tion gases being carried off to the atmosphere,

and the prereduction being effected by means of the excess of theregenerated circulating as. Y

g In the accompanying drawing, I have shown diagrammatically alongitudinal vertical section of a channel furnace adapted for theperformingof the invention.

Referring to the drawing, A designates the introduction end and B thedischarge end of the channel furnace. Nearest to the.introduction end Ais a preheating zone C and then a roasting zone D and a prereductionzone E follow. Through the introduction end carriages made of refractorymaterial and loaded with the ore to be treated are successivelyintroduced into the furnace. The ore loaded on the carriages is,preferably, in the form of pressed cakes or blocks. At T a AND REDUCINGORES 244,962, and in Norway January 29, 1927.

mixture of carbon monoxide and hydrogen obtained from the recarbonizingfurnaces herebelow described is supplied and at F an excess ofpreferably preheated air is supplied by means of which the gas suppliedat T is combusted in the zone D whereupon the combustion gases pass thezone C and escape through the chimney I. In the zone C a preheating ofthe ore takes place by the hot. combust-ion gases and the temperature ofthe ore o0 rises the nearer the carriages come to the inner end of thezones C, D. By this preheating the ore cakes are in well-known mannerconverted into harder briquettes.

The combustion zone is in direct communication with the prereductionzone E. The desulphurized and oxidized incandescent briquettesintroduced in the zone E are here met by the gas introduced at T andcontaining carbon monoxide and hydrogen. The gas 79 is preheated, ifnecessary, before it enters the zone E and its temperature may be, forinstance, 1100 C. As the briquettes already at their entrance into thezone E have a temperature sufliciently high for the reduction thisprocess takes place immediately, apart of the oxygen of the ore beingcombined with a part of the carbon monoxide and hydrogen to carbondioxide and steam respectively.

In the prereduction zonethe briquettes are 3 converted partly to Fe()and partly to spongy lI'OIl. The prereduction zone E is separated fromthe final reduction zone 0 by means of y a shutter a, which can beelevated momentarily when the carriages are moved forward.

In the final reduction zone a current of carbon monoxide and hydrogen isintroduced at H, the temperature of which may be for instance 1000 C. atthe entrance. Said gas flows in the final reduction zone in the samedirection asthe briquettes are moved and is taken out at G. M is a fanfor maintaining the circulation of the gas. As the briquettes still havea temperaturesuitable for the performance of the reduction such processis continued, the remaining oxygen of the briquettes being combined witha part of the carbon monoxide into carbon dioxide and with the hydrogeninto steam. Said reduction ceases, however, when at the prevailingtemperature acorresponding equilibrium is ob- By ashiftable distributionvalve Q air can be supplied to either of the recarbonizing-furnaces andby means of another shiftable valve R the circulating gas can besupplied to the final reduction zone. A valve L distributes thequantities of circulating gas from G to the recarbonizing furnaces P andP at will.

When the valves are in the positions shown in the drawing a portion ofthe circulating gas, which contains hydrogen and carbon.

monoxide and escapes at G, is introduced into P The supply of air isregulated in such manner that said gas is completely combusted. Also aportion of the solid fuel is then combusted by direct combustion withthe air abundantly supplied. CO being substantially formed. Thecombustion gases essentially consisting in (10,, N and H 0 escapethrough the chimney Z Simultaneously the chief part of the circulatinggas is introduced into P and regenerated and finally distributed by thevalve 6.

When the reduction gas is passed through the incandescent carbon layerits content of carbon dioxide is reduced by the carbon into carbonmonoxide and the steam into carbon monoxid and hydrogen, so that the gasescaping-fromthe recarbonizin furnace consists, chiefly, in carbonmonoxide and hydrogen, which through the valve R is returned to thechannel furnace through the gas inlets H i ufid T.

e greater part of the circulating s is introduced in the furnace at H,the re iiiining part which corresponds to the excess, being introducedat T and flowing further on as described above.

The heat, which is necessary for the reaction is taken from the heataccumulated in the fuel. When the temperature of the fuelhas decreasedin such a degree that the formation of carbon monoxide begins to ceasethe valves 0 and R are reversed and the valve L,

ii also adjusted to a new position, if desired, P being thus reheatedand P delivering heat a to the circulating gas.

Before the gas enriched as to carbon monoxide and hydro en is introducedat H, it

can be conveyed t ough a heatipg'apparatus z, for raising itstemperature in a required through. pre

degree. The preheating of the gas introduced at T may take place in aheating ap aratus S while the preheating of the circu ating gas escapingfrom G is erformed in a heating apparatus S before it enters therecarbonizing furnaces.

The cooling of the spongy iron produced may, for instance, be performedby means of a cooling carriage U, which is cooled by means of externalwater sprayers.

When the circulatin gas is removed at G, the cooling of the rea ybriquettes may also be performed by means of water sprayers V at thedischarge end of the channel furnace. At the contact with the hotbriquettes the water is converted into steam, which follows thecirculating gas escaping from the furnace through-the gas outlet G. Theportion ofthe circulating gas, which is introduced into therecarbonizing furnace just operated, has its content of steam convertedinto hydrogen and carbon monoxide according to the formula: 'C+H O=H+CO. The gas supplied into the reduction furnace at'H thus will containa certain percentage of hydrogen. Said percentage of hydrogen may beincreased by direct supply of water through water sprayers, steam jets,or the like into the piping for the circulating gas, as shown at 0.

What I claim is 1. Method of reducing ores, which comprises trans rtingthe ore successively through pre eating, roasting, prereduction andfinal reduction zones of a channel furnace, subjecting the ore in thefinal reduction zone to the reducing action of circulating reducinggases, recarbonizing said gases outside the furnace in alternatelyoperative recarbonizing furnaces containing incandescent layers ofcarbon, reheating the momentarily inoperative recarbonizing furnace by aplentiful supply ofair supplied through its layer of carbon whiledischarging the combustion gases formed into the atmosphere, returning aportion of the recarbonized gases to the final reduction zone, supplyinganother portion thereof to the prereduction zone and finally combustingit by an excess of air in the roasting zone of the channel furnace.

2. Method of reducing ores, which comprises trans rting the oresuccessively and final reduction zones of a channel furnace, subjectinthe ore in the final reduction zone to the ucing action of circulatingreducing gases, recarbonizing said gases outside the channel inalternately operative recarbonizing furnaces containing incandescentlayers of carbon, supplying a portion of the circulatlng gas-to themomentarily inoperative furnace and combusting it therein together witha portion of the solid carbon b a plentiful supply of air for reheatingsaid furnace while discharging the combustion gases formed into theatmosphere, returning a poreating, roasting, prereduction all) tion ofthe recarbonized gases to the final reduction zone, and su plyinganother portion thereof to the prere uction zone and finally combustingit by an excess of air in the roasting zone of the channel furnace.

3. Method of reducing ores, which comprises transporting the oresuccessively through preheating, roasting, prereduction and finalreduction zones of a channel furnace,

subjectin the ore in the final reduction zone 4 to the re ucing actionof circulating reducing gases, mixing the circulating gas escapin fromthe final reduction zone with steam an recarbonizing said mixtureoutside the channel furnace in alternately operative recarbonizingfurnaces containing incandescent layers of carbon, reheating themomentarily inoperative recarbonizing furnace by a plentiful supply ofair supplied throu h its layer of carbon while discharging t ecombustion gases formed into the atmosphere, returningv a portiomof therecarbonizing gases to the final reduction zone, and supplying anotherportion thereof to the prereduction zone and finallycombustin it by anexcess of air in the roasting zone of t e channel furnace.

4. Method of reducing ores, which comprises transporting the oresuccessively through preheating, roasting, prereduction and finalreduction zones of a channel furnace, subjecting the ore in the finalreduction zone to the reducing action of circulating reducing gases,cooling the reduced ore by water sprays, drawing oil the steam formedtogether with the reducing gases from the final reduction zone andrecarbonizing said mixture outside the channel furnace in alternatelyopera;

tive recarbonizing furnaces containing incandescent layers of carbon,reheating the moinentarily inoperative recarbonizing furnace by aplentiful supply of air supplied through its layer of carbon whiledischarging the .combustion gases formed into the atmosphere,

returning a portion of the recarbonized gases to the final reductionzone, and supplying another portion thereof to the prereduction zonetill) and finally combusting it by an excess'of air in the roasting zoneof the channel furnace. In testimony whereof I have signed my name.

BROR GHRISTIANSEN.

